1. Field of the Invention
The present invention generally relates to continuously variable V-belt transmissions. More specifically, the present invention relates to determining the thrust to be applied to a pulley of a continuously variable V-belt transmission.
2. Background Information
Conventional continuously variable V-belt transmissions basically have a driving pulley that receive an input torque from the engine, a driven pulley that outputs torque to a drive wheel and a V-belt that winds around the driving and driven pulleys to transmit rotation from the driving pulley to the driven pulley. In particular, the input torque to the driving pulley is transmitted from the driving pulley to the V-belt due to the friction between a pair of sheave faces of the driving pulley pressing against the V-belt. The V-belt then transmits the torque to the driven pulley due to the friction between a pair of sheave faces of the driven pulley pressing against the V-belt. The V-belt typically has a plurality of elements and a ring interconnecting the elements. When the sheave faces of the driving pulley pressing against the V-belt, each element of the V-belt is pushed out of the driving pulley to rotate the V-belt, the friction force between each element and the ring interconnecting the elements. This rotation of the V-belt results in a difference between the tensile force acting on the ring on the compression side and the tensile force acting on the ring on the stretch (tension) side.
The thrust with which a pulley is pressed against a V-belt is calculated by adding a thrust difference required to obtain a desired value of a pulley ratio to a value that has been set by multiplying a safety factor with a minimum thrust, which varies with different input torques, required to ensure that the V-belt will not slip. An example of such a continuously variable V-belt transmission is disclosed in Japanese Laid-Open Patent Publication No. 2000-18347A, which corresponds to U.S. Pat. No. 6,135,915.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved continuously variable V-belt transmission. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.